Carboniferous

“ But equally certain it is, I repeat, that wherever carboniferous formations have been discovered and examined, they have been found to bear the unique characteristic to which the system owes its name,—they have been found charged with the carbon, existing usually as great beds of coal, which was elaborated of old by its unrivalled flora from the elements. ”

“ Rarely are any large trunks or branches observable in the beds of coal; but the general appearance of the carboniferous mass is that of an immense deposit of delicate foliage shed and accumulated in a forest, and consolidated by great pressure while undergoing that peculiar process by which vegetable matter is converted into carbon. ”

“ In our survey of the Carboniferous age, though there are peculiarities in the life of its older, middle, and newer divisions, we may take the great coal measures of the middle portion as the type of the land life of the period, and the great limestones of the lower portion as that of the marine life ”

“ The great carboniferous formation may be subdivided into four orders of rocks: 1. the coal-measures, including their manifold alternations of coal-beds, sandstones, and shales; 2. the millstone grit and shale towards the bottom of the coal-measures; 3. the carboniferous limestone, which projecting to considerable heights above the outcrop of the coal and grit, acquires the title of mountain limestone; 4. the old red sandstone, or connecting link with the transition and primary rock basin in which the coal system lies. ”

“ Some features of the condition of the earth during the deposition of the carboniferous group, are made out with a clearness which must satisfy most minds. First we are told of a time when carbonate of lime was formed in vast abundance at the bottoms of profound seas, accompanied by an unusually large population of corals and encrinites; while in some parts of the earth there were patches of dry land, covered with a luxuriant vegetation. ”

“ It is to be admitted for strict truth that, in some parts of Europe, the carboniferous formation is followed by superior deposits, without the appearance of such disturbances between their respective periods; but apparently this case belongs to the class of exceptions already noticed. [93] That disturbance was general, is supported by the further and important fact of the destruction of many forms of organic being previously flourishing, particularly of the vegetable kingdom. ”

“ The great forests of the Carboniferous epoch now exists as beds of coal. By the burning of coal--a chemical transformation--the heat energy is produced on which at present our whole civilisation depends. Whence is the energy locked up in the coal derived? From the sun. For millions of years the energy of the sun's rays had gone to form the vast vegetation of the Carboniferous era and had been transformed, by various subtle processes, into the potential energy that slumbers in those immense fossilized forests. ”

“ The abundant life of the Carboniferous period was succeeded by a vast cycle of dry and bitter ages. They are represented in the Record of the Rocks by thick deposits of sandstones and the like, in which fossils are comparatively few. The temperature of the world fluctuated widely, and there were long periods of glacial cold. Over great areas the former profusion of swamp vegetation ceased, and, overlaid by these newer deposits, it began that process of compression and mineralization that gave the world most of the coal deposits of to-day. ”

“ In the north of England, for example, the thickness of the coal-bearing strata has been estimated at 3000 feet, while the various coal-seams, 20 or 30 in number, do not in the aggregate exceed 60 feet. [308-A]
The carboniferous formation comprises two very distinct members: 1st, that usually called the Coal-measures, of mixed freshwater, terrestrial, and marine origin, often including seams of coal; 2dly, that named in England the Mountain or Carboniferous limestone, of purely marine origin, and containing corals, shells, and encrinites. ”

“ If you like, on the other hand, to be scientific you will listen to those who tell you that instead of there having been one unique carboniferous epoch, with a peculiar coal-making climate, all epochs are carboniferous if they get the chance; that coal is of every age, from that of the Scotch and English beds, up to the present day. The great coal-beds along the Rocky Mountains, for instance, are tertiary—that is, later than the chalk. ”

“ In subdividing the strata of the Carboniferous system and correlating the major divisions in different areas, just as in other great systems, use has to be made of the fossil contents of the rocks; stratigraphical units, based on lithology, are useless for this purpose. The groups of organisms utilized for zoning and correlation by different workers include brachiopods, pelecypods, cephalopods, corals, fishes and plants; and the results of the comparison of the faunas and floras of different areas where Carboniferous rocks occur are generalized in the table below. ”

“ Though there is great diversity in the Carboniferous coals, and it would be absurd to express their composition by a single formula, it may be said that, over the whole world, these coals have characteristics, as a group, by which they can be recognized, the result of the slow decomposition of the tissue of plants which lived in the Carboniferous age, and which have, by a broad and general change, approximated to a certain phase in the spontaneous distillation of plant-tissue. ”

“ That age of the world’s history which, from its richness in accumulations of vegetable matter destined to be converted into coal, has been named the Carboniferous, is in relation to living beings the most complete and noble of the Palæozoic periods. ”

“ Succession and Thickness of Strata.
Considered in its greatest generality, and with reference to countries where the masses appear in the greatest simplicity (as in the south of England) , the carboniferous system consists of three formations: viz.—
Coal formation. ”

“ The greatest development of vegetable life was, however, during the carboniferous period. The design of this abundant growth was prospective. It was not produced for the support of animal life, but for fuel, and stored till man should be introduced, and so far advanced in civilization as to make this supply of carbonaceous matter subservient to his wants and happiness. ”

“ It was during the Carboniferous epoch, when our principal and most valuable seams of coal were deposited, that all these favorable circumstances were in their highest development. For a dense vegetation we also want a warm, moist, and equable climate, and air more or less charged with carbonic-acid gas, as that is the food of plants (just as the oxygen gives life to man) , though it is poisonous to warm-blooded animals, it being impossible for such to live in an atmosphere containing more than about one per cent. ”

“ In a word, all the indications suggest the early and middle Carboniferous as an age of vast swamps, of enormous stretches of land just above or below the sea-level, and changing repeatedly from one to the other. ”

“ It seems strange to one who derives his supply of domestic fuel from the Dalkeith and Falkirk coal-fields, that the Carboniferous flora could ever have been described as devoid of trees. I can scarce take up a piece of coal from beside my study fire, without detecting in it fragments of carbonized wood, which almost always exhibit the characteristic longitudinal fibres, and not unfrequently the medullary rays. ”

“ Carboniferous, Europe and North America. Firs, and possibly by the Cycads or "false palms." [18] Amongst the "Cryptogams," there is no more striking or beautiful group of Carboniferous plants than the Ferns. Remains of these are found all through the Carboniferous, but in exceptional numbers in the Coal-measures, and include both herbaceous forms like the majority of existing species, and arborescent forms resembling the living Tree-ferns of New Zealand. ”

“ Observations of geological strata indicate an increase of carbon in the crust of the earth since the earliest times, for the rocks of the older formations contain less of it than those of the carboniferous and succeeding ones. ”

“ It has often been suggested that, during the Carboniferous period, the atmosphere must have been warmer and more charged with aqueous vapour and carbon dioxide than at the present day, to admit of so luxuriant a flora as that from which the coal-seams were formed. There seems, however, to be at present no method of arriving at any certainty on this subject. Lastly, the amount of carbonic acid absorbed in the weathering of rocks at the surface, and the consequent production of carbonates, represents an enormous abstraction of this gas. ”

“ The Carboniferous period has been so named because at that time the climate and features of the earth in many places favored the growth of dense and heavy vegetation. This vegetation accumulated through the long years, so that it formed thick deposits which gradually changed to beds of coal. It would be wrong, however, to think that all the beds of coal were formed at about the same time. Ever since there have been forests and marshes upon the earth there have been opportunities for the forming of coal-beds. Materials are accumulating even now which will in time be transformed to beds of coal. ”

“ The purity of the coal, or its non-intermixture with earthy matter, presents another theoretical difficulty to many geologists, who are inclined to believe that the trees and smaller plants of the carboniferous period grew in extensive swamps, rather than on land not liable to be inundated. ”

“ Aix-la-Chapelle.—The Kaiserquelle rises at the junction of clay slate and carboniferous limestone, with a temperature 85° above that of the vicinity; contains of saline ingredients 32 grains in a pint (muriate, carbonate, and sulphate of soda, &c.) ; evolves nitrogen 69.5, and carbonic acid 30.
Borset.—The Mühlenbend rises with the same geological relations as the last, with a temperature 121.5° above that of the place; contains of saline ingredients 34 grains in a pint (muriate, carbonate, and sulphate of soda, &c.) ; evolves nitrogen 80 per cent., oxygen 2, and carbonic acid 18. ”

“ The waters had now brought forth abundantly the moving creatures, which, at first more scantily distributed, produced the limestone of the silurian rocks, as the arborial remains of the land, in like stinted measure, are inclosed in the older palæozoic deposits. Their day of increase as it advanced, each after their kind, is recorded in the vast accumulations [100] of animal and vegetable matter which compose the strata of the carboniferous system, both of an order and quality purposely so arranged, and never upon the same scale of magnitude to be repeated in the combustible mineral. ”

“ Organic Remains.—The forms of life buried in the carboniferous system of strata are exceedingly numerous and varied, and, being generally in an excellent state of preservation, allow of a most strict comparison with existing types. They consist of very many races of plants, abundance of zoophyta, multitudes of mollusca, some Crustacea, many fishes, but, as far as we yet know, neither reptiles, birds, nor mammalia. Many of the plants, indeed by far the greater number, are of terrestrial growth: all the zoophyta, and nearly all the mollusca, Crustacea, and fishes, are marine. ”

“ Carboniferous strata in the south-west of England — Superposition of Coal-measures to Mountain limestone — Departure from this type in north of England and Scotland — Section in South Wales — Underclays with Stigmaria — Carboniferous Flora — Ferns, Lepidodendra, Calamites, Asterophyllites, Sigillariæ, Stigmariæ, — Coniferæ — Endogens — Absence of Exogens — Coal, how formed — Erect fossil trees — Parkfield Colliery — St. ”

“ The growth of forests, and the produce of meadows, demonstrate that an inexhaustible quantity of carbon is furnished for vegetation by the carbonic acid of the atmosphere.
We obtain from an equal surface of forest, or meadow-land, where the necessary mineral elements of the soil are present in a suitable state, and to which no carbonaceous matter whatever is furnished in manures, an amount of carbon, in the shape of wood and hay, quite equal, and oftimes more than is produced by our fields, in grain, roots, and straw, upon which abundance of manure has been heaped. ”

“ We can scarcely, therefore, expect that the vegetable world had made any great advance in complexity of organism at this time, otherwise the supplies of graphite or plumbago which are found in the formation, would be attributed to dense forest growths, acted upon, after death, in a similar manner to that which awaited the vegetation which, ages after, went to form beds of coal. At present we know of no source of carbon except through the intervention and the chemical action of plants. Like iron, carbon is seldom found on the earth except in combination. ”

“ The vast quantities of carbon dioxide afterwards sealed up in limestones and carbonaceous beds must also have still floated in the atmosphere and must have supplied abundance of the carbon, which constitutes the largest ingredient in vegetable tissues. Under these circumstances the whole world must have resembled a damp, warm greenhouse, and plants loving such an atmosphere could have grown luxuriantly. In these circumstances the lower forms of aquatic vegetation and those that love damp, warm air and wet soil would have been at home. ”

“ The atmosphere contains a small quantity of carbonic dioxide, and the soil a larger quantity, the result of vegetable decomposition. Rain water absorbs some of it, and carries it into the rocks, as it soaks into the ground. This gas has the property of combining with carbonate of lime,—the material of which shells and limestone are made. The bicarbonate of lime so formed is soluble in water, which is not the case with the simple carbonate. Water containing carbonic dioxide soaking into a limestone rock or a mass of shells dissolves some of the carbonate of lime, and carries it on with it. ”